Heart wall tension reduction apparatus

ABSTRACT

An apparatus for treatment of a failing heart by reducing the wall tension therein. In one embodiment, the apparatus includes a tension member for drawing at least two walls of a heart chamber toward each other.

FIELD OF THE INVENTION

[0001] The present invention pertains to the field of apparatus fortreatment of a failing heart. In particular, the apparatus of thepresent invention is directed toward reducing the wall stress in thefailing heart.

BACKGROUND OF THE INVENTION

[0002] The syndrome of heart failure is a common course for theprogression of many forms of heart disease. Heart failure may beconsidered to be the condition in which an abnormality of cardiacfunction is responsible for the inability of the heart to pump blood ata rate commensurate with the requirements of the metabolizing tissues,or can do so only at an abnormally elevated filling pressure. There aremany specific disease processes that can lead to heart failure with aresulting difference in pathophysiology of the failing heart, such asthe dilatation of the left ventricular chamber. Etiologies that can leadto this form of failure include idiopathic cardiomyopathy, viralcardiomyopathy, and ischemic cardiomyopathy.

[0003] The process of ventricular dilatation is generally the result ofchronic volume overload or specific damage to the myocardium. In anormal heart that is exposed to long term increased cardiac outputrequirements, for example, that of an athlete, there is an adaptiveprocess of slight ventricular dilation and muscle myocyte hypertrophy.In this way, the heart fully compensates for the increased cardiacoutput requirements. With damage to the myocardium or chronic volumeoverload, however, there are increased requirements put on thecontracting myocardium to such a level that this compensated state isnever achieved and the heart continues to dilate.

[0004] The basic problem with a large dilated left ventricle is thatthere is a significant increase in wall tension and/or stress bothduring diastolic filling and during systolic contraction. In a normalheart, the adaptation of muscle hypertrophy (thickening) and ventriculardilatation maintain a fairly constant wall tension for systoliccontraction. However, in a failing heart, the ongoing dilatation isgreater than the hypertrophy and the result is a rising wall tensionrequirement for systolic contraction. This is felt to be an ongoinginsult to the muscle myocyte resulting in further muscle damage. Theincrease in wall stress is also true for diastolic filling.Additionally, because of the lack of cardiac output, there is generallya rise in ventricular filling pressure from several physiologicmechanisms. Moreover, in diastole there is both a diameter increase anda pressure increase over normal, both contributing to higher wall stresslevels. The increase in diastolic wall stress is felt to be the primarycontributor to ongoing dilatation of the chamber.

[0005] Prior art treatments for heart failure fall into three generallycategories. The first being pharmacological, for example, diuretics. Thesecond being assist systems, for example, pumps. Finally, surgicaltreatments have been experimented with, which are described in moredetail below.

[0006] With respect to pharmacological treatments, diuretics have beenused to reduce the workload of the heart by reducing blood volume andpreload. Clinically, preload is defined in several ways including leftventricular end diastolic pressure (LVEDP), or left ventricular enddiastolic volume (LVEDV). Physiologically, the preferred definition isthe length of stretch of the sarcomere at end diastole. Diuretics reduceextra cellular fluid which builds in congestive heart failure patientsincreasing preload conditions. Nitrates, arteriolar vasodilators,angiotensin converting enzyme inhibitors have been used to treat heartfailure through the reduction of cardiac workload through the reductionof afterload. Afterload may be defined as the tension or stress requiredin the wall of the ventricle during ejection. Inotropes like digoxin arecardiac glycosides and function to increase cardiac output by increasingthe force and speed of cardiac muscle contraction. These drug therapiesoffer some beneficial effects but do not stop the progression of thedisease.

[0007] Assist devices include mechanical pumps and electricalstimulators. Mechanical pumps reduce the load on the heart by performingall or part of the pumping function normally done by the heart.Currently, mechanical pumps are used to sustain the patient while adonor heart for transplantation becomes available for the patient.Electrical stimulation such as bi-ventricular pacing have beeninvestigated for the treatment of patients with dilated cardiomyopathy.

[0008] There are at least three surgical procedures for treatment ofheart failure: 1) heart transplant; 2) dynamic cardiomyoplasty; and 3)the Batista partial left ventriculectomy. Heart transplantation hasserious limitations including restricted availability of organs andadverse effects of immunosuppressive therapies required following hearttransplantation. Cardiomyoplasty includes wrapping the heart withskeletal muscle and electrically stimulating the muscle to contractsynchronously with the heart in order to help the pumping function ofthe heart. The Batista partial left ventriculectomy includes surgicallyremodeling the left ventricle by removing a segment of the muscularwall. This procedure reduces the diameter of the dilated heart, which inturn reduces the loading of the heart. However, this extremely invasiveprocedure reduces muscle mass of the heart.

SUMMARY OF THE INVENTION

[0009] The present invention pertains to a non-pharmacological, passiveapparatus for the treatment of a failing heart. The device is configuredto reduce the tension in the heart wall. It is believed to reverse, stopor slow the disease process of a failing heart as it reduces the energyconsumption of the failing heart, decrease in isovolumetric contraction,increases sarcomere shortening during contraction and an increase inisotonic shortening in turn increases stroke volume. The device reduceswall tension during diastole (preload) and systole.

[0010] In one embodiment, the apparatus includes a tension member fordrawing at least two walls of the heart chamber toward each other toreduce the radius or area of the heart chamber in at least one crosssectional plane. The tension member has anchoring member disposed atopposite ends for engagement with the heart or chamber wall.

[0011] In another embodiment, the apparatus includes a compressionmember for drawing at least two walls of a heart chamber toward eachother. In one embodiment, the compression member includes a balloon. Inanother embodiment of the apparatus, a frame is provided for supportingthe compression member.

[0012] Yet another embodiment of the invention includes a clamp havingtwo ends biased toward one another for drawing at least two walls of aheart chamber toward each other. The clamp includes at least two endshaving atraumatic anchoring member disposed thereon for engagement withthe heart or chamber wall.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a transverse cross-section of the left and rightventricles of a human heart showing the placement of a splint inaccordance with the present invention;

[0014]FIG. 2 is a transverse cross-section of the left and rightventricles of a human heart showing the placement of a balloon device inaccordance with the present invention;

[0015]FIG. 3 is a transverse cross-section of the left and rightventricles of a human heart showing the placement of an externalcompression frame structure in accordance with the present invention;

[0016]FIG. 4 is a transverse cross-section of the left and rightventricles of a human heart showing a clamp in accordance with thepresent invention;

[0017]FIG. 5 is a transverse cross-section of the left and rightventricles of a human heart showing a three tension member version ofthe splint of FIG. 1;

[0018]FIG. 6 is a transverse cross-section of the left and rightventricles of a human heart showing a four tension member version of thesplint shown in FIG. 1;

[0019]FIG. 7 is a vertical cross-section of the left ventricle andatrium, the left ventricle having scar tissue;

[0020]FIG. 8 is a vertical cross-section of the heart of FIG. 7 showingthe splint of FIG. 1 drawing the scar tissue toward the opposite wall ofthe left ventricle;

[0021]FIG. 9 is a vertical cross-section of the left ventricle andatrium of a human heart showing a version of the splint of FIG. 1 havingan elongate anchor bar;

[0022]FIG. 10 is a side view of an undeployed hinged anchor member;

[0023]FIG. 11 is a side view of a deployed hinged anchor member of FIG.10;

[0024]FIG. 12 is a cross-sectional view of an captured ball anchormember;

[0025]FIG. 13 is a perspective view of a cross bar anchor member;

[0026]FIG. 14 is a idealized cylindrical model of a left ventricle of ahuman heart;

[0027]FIG. 15 is a splinted model of the left ventricle of FIG. 14;

[0028]FIG. 16 is a transverse cross-sectional view of FIG. 15 showingvarious modeling parameters;

[0029]FIG. 17 is a transverse cross-section of the splinted leftventricle of FIG. 15 showing a hypothetical force distribution; and

[0030]FIG. 18 is a second transverse cross-sectional view of the modelleft ventricle of FIG. 15 showing a hypothetical force distribution.

DETAILED DESCRIPTION OF THE INVENTION

[0031] Referring now to the drawings wherein like reference numeralsrefer to like elements throughout the several views, FIG. 1 shows atransverse cross-section of a left ventricle 10 and a right ventricle 12of a human heart 14. Extending through the left ventricle is a splint 16including a tension member 18 and oppositely disposed anchors 20. Splint16 as shown in FIG. 1 has been positioned to draw opposite walls of leftventricle 10 toward each other to reduce the “radius” of the leftventricular cross-section or the cross-sectional area thereof to reduceleft ventricular wall stresses. It should be understood that althoughthe splint 16 and the alternative devices disclosed herein are describedin relation to the left ventricle of a human heart, these devices couldalso be used to reduce the radius or cross-sectional area of the otherchambers of a human heart in transverse or vertical directions, or at anangle between the transverse and vertical.

[0032]FIG. 2 discloses an alternate embodiment of the present invention,wherein a balloon 200 is deployed adjacent the left ventricle. The sizeand degree of inflation of the balloon can be varied to reduce theradius or cross-sectional area of left ventricle 10 of heart 14.

[0033]FIG. 3 shows yet another alternative embodiment of the presentinvention deployed with respect to left ventricle 10 of human heart 14.Here a compression frame structure 300 is engaged with heart 14 atatraumatic anchor pads 310. A compression member 312 having anatraumatic surface 314 presses against a wall of left ventricle 10 toreduce the radius or cross-sectional area thereof.

[0034]FIG. 4 is a transverse cross-sectional view of human heart 14showing yet another embodiment of the present invention. In this case aclamp 400 having atraumatic anchor pads 410 biased toward each other isshown disposed on a wall of left ventricle 10. Here the radius orcross-sectional area of left ventricle 10 is reduced by clamping off theportion of the wall between pads 410. Pads 410 can be biased toward eachother and/or can be held together by a locking device.

[0035] Each of the various embodiments of the present inventiondisclosed in FIGS. 1-4 can be made from materials which can remainimplanted in the human body indefinitely. Such biocompatible materialsare well-known to those skilled in the art of clinical medical devices.

[0036]FIG. 5 shows an alternate embodiment of the splint of FIG. 1referred to in FIG. 5 by the numeral 116. The embodiment 116 shown inFIG. 5 includes three tension members 118 as opposed to a single tensionmember 18 as shown in FIG. 1. FIG. 6 shows yet another embodiment of thesplint 216 having four tension members 218. It is anticipated that insome patients, the disease process of the failing heart may be soadvanced that three, four or more tension members may be desirable toreduce the heart wall stresses more substantially than possible with asingle tension member as shown in FIG. 1.

[0037]FIG. 7 is a partial vertical cross-section of human heart 14showing left ventricle 10 and left atrium 22. As shown in FIG. 7, heart14 includes a region of scar tissue 24 associated with an aneurysm orischemia. As shown in FIG. 7, the scar tissue 24 increases the radius orcross-sectional area of left ventricle 10 in the region affected by thescar tissue. Such an increase in the radius or cross-sectional area ofthe left ventricle will result in greater wall stresses on the walls ofthe left ventricle.

[0038]FIG. 8 is a vertical cross-sectional view of the heart 14 as shownin FIG. 7, wherein a splint 16 has been placed to draw the scar tissue24 toward an opposite wall of left ventricle 10. As a consequence ofplacing splint 16, the radius or cross-sectional area of the leftventricle affected by the scar tissue 24 is reduced. The reduction ofthis radius or cross-sectional area results in reduction in the wallstress in the left ventricular wall and thus improves heart pumpingefficiency.

[0039]FIG. 9 is a vertical cross-sectional view of left ventricle 10 andleft atrium 22 of heart 14 in which a splint 16 has been placed. Asshown in FIG. 9, splint 16 includes an alternative anchor 26. The anchor26 is preferably an elongate member having a length as shown in FIG. 9substantially greater than its width (not shown). Anchor bar 26 might beused to reduce the radius or cross-sectional area of the left ventriclein an instance where there is generalized enlargement of left ventricle10 such as in idiopathic dilated cardiomyopathy. In such an instance,bar anchor 26 can distribute forces more widely than anchor 20.

[0040]FIGS. 10 and 11 are side views of a hinged anchor 28 which couldbe substituted for anchors 20 in undeployed and deployed positionsrespectively. Anchor 28 as shown in FIG. 10 includes two legs similar tobar anchor 26. Hinged anchor 28 could include additional legs and thelength of those legs could be varied to distribute the force over thesurface of the heart wall. In addition there could be webbing betweeneach of the legs to give anchor 28 an umbrella-like appearance.Preferably the webbing would be disposed on the surface of the legswhich would be in contact with the heart wall.

[0041]FIG. 12 is a cross-sectional view of a capture ball anchor 30.Capture ball anchor 30 can be used in place of anchor 20. Capture ballanchor 30 includes a disk portion 32 to distribute the force of theanchor on the heart wall, and a recess 34 for receiving a ball 36affixed to an end of tension member 18. Disk 32 and recess 34 include aside groove which allows tension member 38 to be passed from an outsideedge of disk 32 into recess 34. Ball 36 can then be advanced into recess34 by drawing tension member 18 through an opening 38 in recess 34opposite disk 32.

[0042]FIG. 13 is a perspective view of a cross bar anchor 40. The crossbar anchor 40 can be used in place of anchors 20. The anchor 40preferably includes a disk or pad portion 42 having a cross bar 44extending over an opening 46 in pad 42. Tension member 18 can beextended through opening 46 and tied to cross bar 42 as shown.

[0043] In use, the various embodiments of the present invention areplaced in or adjacent the human heart to reduce the radius orcross-section area of at least one chamber of the heart. This is done toreduce wall stress or tension in the heart or chamber wall to slow, stopor reverse failure of the heart. In the case of the splint 16 shown inFIG. 1, a canula can be used to pierce both walls of the heart and oneend of the splint can be advanced through the canula from one side ofthe heart to the opposite side where an anchor can be affixed ordeployed. Likewise, an anchor is affixed or deployed at the opposite endof splint 16.

[0044]FIG. 14 is a view of a cylinder or idealized heart chamber 48which is used to illustrate the reduction of wall stress in a heartchamber as a result of deployment of the splint in accordance with thepresent invention. The model used herein and the calculations related tothis model are intended merely to illustrate the mechanism by which wallstress is reduced in the heart chamber. No effort is made herein toquantify the actual reduction which would be realized in any particularin vivo application.

[0045]FIG. 15 is a view of the idealized heart chamber 48 of FIG. 14wherein the chamber has been splinted along its length L such that a“figure eight” cross-section has been formed along the length thereof.It should be noted that the perimeter of the circular transversecross-section of the chamber in FIG. 14 is equal to the perimeter of thefigure eight transverse cross-section of FIG. 15. For purposes of thismodel, opposite lobes of the figure in cross-section are assumed to bemirror images.

[0046]FIG. 16 shows various parameters of the FIG. 8 cross-section ofthe splinted idealized heart chamber of FIG. 15. Where l is the lengthof the splint between opposite walls of the chamber, R₂ is the radius ofeach lobe, θ is the angle between the two radii of one lobe whichextends to opposite ends of the portion of the splint within chamber 48and h is the height of the triangle formed by the two radii and theportion of the splint within the chamber 48 (R₁ is the radius of thecylinder of FIG. 14). These various parameters are related as follows:

h=R ₂ COS(θ/2)

l=2R ₂ SIN(θ/2)

R ₂ =R ₁π/(2π−θ)

[0047] From these relationships, the area of the figure eightcross-section can be calculated by:

A ₂=2π(R ₂)²(1−θ/2π)+hl

[0048] Where chamber 48 is unsplinted as shown in FIG. 14 A₁, theoriginal cross-sectional area of the cylinder is equal to A₂ whereθ=180°, h=0 and l=2R₂. Volume equals A₂ times length L andcircumferential wall tension equals pressure within the chamber times R₂times the length L of the chamber.

[0049] Thus, for example, with an original cylindrical radius of fourcentimeters and a pressure within the chamber of 140 mm of mercury, thewall tension T in the walls of the cylinder is 104.4 newtons. When a3.84 cm splint is placed as shown in FIGS. 15 and 16 such that l=3.84cm, the wall tension T is 77.33 newtons.

[0050]FIGS. 17 and 18 show a hypothetical distribution of wall tension Tand pressure P for the figure eight cross-section. As θ goes from 180°to 0°, tension T_(s) in the splint goes from 0 to a 2T load where thechamber walls carry a T load.

[0051] It will be understood that this disclosure, in many respects, isonly illustrative. Changes may be made in details, particularly inmatters of shape, size, material, and arrangement of parts withoutexceeding the scope of the invention. Accordingly, the scope of theinvention is as defined in the language of the appended claims

What is claimed is:
 1. An apparatus for the treatment of a failingheart, comprising: means for reducing the cross sectional area of theheart in at least one plane.
 2. The apparatus of claim 1, wherein themeans includes a tension member for drawing at least two walls of theheart chamber toward each other.
 3. The apparatus of claim 1, whereinthe means includes a compression member for urging at least two walls ofthe heart chamber toward each other.
 4. The apparatus in accordance withclaim 3, wherein the compression member includes a balloon.
 5. Theapparatus in accordance with claim 3, wherein the means furthercomprises a frame for supporting the compression member.
 6. Theapparatus in accordance with claim 1, wherein the means includes aclamp.
 7. An apparatus for reducing the tension in the wall of the heartchamber in at least one cross sectional plane, comprising: a draw memberhaving first and second ends; and anchoring means disposed at each endof the draw member for engagement with the chamber wall.
 8. An apparatusin accordance with claim 7, wherein the draw member includes a tensionmember.
 9. The apparatus in accordance with claim 7, wherein the drawmember includes a clamp.
 10. The apparatus in accordance with claim 9,wherein the anchor members are biased toward each other.
 11. Anapparatus for reducing the tension in the wall of a heart chamber in atleast one cross sectional plane, comprising: a compression member havingan atraumatic surface for placement against the exterior of the heart.12. The apparatus in accordance with claim 11, wherein the compressionmember includes a balloon.
 13. The apparatus in accordance with claim11, further comprising a frame for supporting the compression member.14. The apparatus in accordance with claim 13, wherein the frameincludes means for attachment of the frame to the heart.